The present invention relates generally to designating a control channel in a telecommunications system.
Telecommunications terminals connect subscriber lines, such as POTS (Plain Old Telephone Service) lines, ISDN (Integrated Services Digital Network) lines, E1 (Electronic Interface Level 1) lines, and optics lines to telecommunications exchanges and other telecommunications equipment. A terminal contains channel unit card slots that accept channel unit cards. The channel unit cards, or line cards, convert analog or digital signals from subscriber lines into formatted digital data signals. Different types of channel unit cards service different types of subscriber lines.
A terminal constructs a single time division multiplexed (TDM) signal from several channel unit cards' formatted digital data signals for transmission to remote telecommunications equipment. The terminal also demultiplexes TDM signals received from remote telecommunications equipment to deliver formatted digital data back to the channel unit cards. Channel unit cards convert the formatted digital data into a form suitable for transmission over subscriber lines.
Two telecommunications terminals can be connected "back to back" to form a digital carrier loop network. A digital carrier loop network typically includes a remote terminal placed near a business or residence and a central terminal placed in a central exchange connected to a telecommunications switch. The remote terminal and central terminal communicate over one or more lines carrying TDM signals. This configuration connects subscribers to the telecommunications switch.